Humongousaur is one of the ten new alien forms that an older Ben gains from a recalibrated Omnitrix. He is the 3rd new alien that Ben uses. Humongosaur is a Vaxasaurian from the planet Terradino. Terradino is described as a postcard paradise with sandy beaches and thick jungles.
Ben first transforms into Humugosaur in Ben 10 Returns (Part 2) when the Omnitrix is recalibrated.
He has great strength and the ability to change his body's size from a regular size to a giant size. He also becomes stronger as he grows. When he becomes large enough, he grows more and more dinosaur-like. Ben takes on Humongousaur as his new "big guns" in place of Fourarms. The large and increasing size probably comes from Way Big.
Growing is only possible in large areas, if he is in an area smaller than what he would grow to, he cannot grow. Overall, Ben is much clumsier in this form. He is not clever being Humongousaur.
Humongousaur is a Vaxasaurian dinosaur-like humanoid from Terradino.